Fuel injection system for internal combustion engines

ABSTRACT

In the suction tube of an internal combustion engine there is disposed a regulator member which is displaceable by air pressure against the force of a return spring tensioned as a function of engine temperatures. Said regulator member is associated with a fuel metering device to vary the proportion of fuel in the fuelair mixture. The fuel quantities are also varied as a function of an arbitrarily set butterfly valve disposed in the suction tube.

United States Patent [72] Inventors Gerhard Stumpp Stuttgart;Klaus-Jurgen Peters, Affalterbach, both of Germany [2 1 Appl. No.884,206

[22] Filed Dec. 11, 1969 [45] Patented Oct. 19, 1971 [73] AssigneeRobert Bosch GmbH Stuttgart, Germany [32] Priority Dec. 14, 1968 [33]Germany [54] FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES 6Claims, 9 Drawing Figs.

[52] US. Cl 123/119, 123/139 AW, 123/139 80, 123/140 CC, 123/140 FG,261/39 A, 261/50 A [51 Int. Cl ..F02n 69/00, F02d 3/02 [50] FieldofSearch 123/119, 139 AW, 139 B0, 140 CC, 140 PG; 261/50 A, 50

AA, 39 A, 39 B [56] References Cited UNITED STATES PATENTS 2,098,202 1H1937 Weber 2,128,079 8/1938 Dawes 2,523,798 9/1950 Winkler 2,583,4061/1952 Arnold 2,774,343 12/1956 Schafferetal .13.

Primary Examiner-Wendell E. Burns Attorney Edwin E. Greigg 261/50 AA261/50 AA 261/50 AA 261/50 AA ABSTRACT: In the suction tube of aninternal combustion engine there is disposed a regulator member which isdisplaceable by air pressure against the force of a return springtensioned as a function of engine temperatures. Said regulator member isassociated with a fuel metering device to vary the proportion of fuel inthe fuel-air mixture. The fuel quantities are also varied as a functionof an arbitrarily set butterfly valve disposed in the suction tube.

PATENTEDUCT 19 I971 SHEET 8 0F 7 5P 5 w w; W mama 4 w. 6 m

BACKGROUND OF THE INVENTION This invention relates to a fuel injectionsystem for externally ignited internal combustion engines of automotivevehicles and is of the type wherein the supply of air is controlled byan arbitrarily operable butterfly valve disposed in the suction tube.The intake air flows past a regulator member which is responsive to thepressure (particularly the dynamic pressure) of the air in the suctiontube, and which is disposed at least partially inside the suction tubeand is displaceable against the force of a return spring. The positionof the regulator member is a function of the flow rate of air determinedby the setting of said butterfly valve. The regulator member, by virtueof its displacement, automatically determines a flow passage section inthe suction tube and, according to said flow passage section, meters thefuel continuously by varying an adjustable throttle through which thefuel flows with a constant pressure drop.

The purpose of a fuel injection system of the aforenoted type is toautomatically provide, in an Otto-engine, in all operational ranges afavorable ratio of fuel-air mixture in order to achieve a possiblycomplete combustion of the fuel and thereby ensure the highest possibleefficiency of the engine, a lowest possible fuel consumption and furtherensure that the generation-of poisonous exhaust gases is eliminated orat least very substantially reduced. For this purpose the fuel quantityhas to be very accurately metered for each operational range of theengine. Conventionally, the butterfly valve is arbitrarily set dependentupon the required power, while the regulator assembly has the functionto meter the fuel for obtaining the optimal ratio of fuel-air mixture.

In known fuel injection systems of the above-discussed type, asdisclosed, for example, in British Pat. No. 1,066,721, the fuel ismetered in the aforeoutlined manner as a function of the flow rate ofair in the suction tube. Since it is insufficient to set a constantfuel-air ratio for each operational range of the engine, this ratio isadjusted to the operational conditions by means of additional devices,for example, by increasing the fuel proportion for large loads or aslong as the engine operates below a desired temperature. In such knownfuel injection systems, the ratio control of the fuel-air mixture isperfonned A. by a pressure-sensitive regulator member disposed upstreamof the butterfly valve and displaceable against the force of a spring tocontrol automatically the effective flow passage section of a variablechannel in the suction tube and to simultaneously control the flowpassage section of a fuel-metering nozzle, and

B. by pressure control means, which under constant rpm. and identicalload conditions maintain a constant pressure drop at the meteringnozzle, but which, however, alter such pressure drop for enriching themixture, for example, when the engine runs cold.

A variation of the fuel proportion of the fuel-air mixture by changingthe pressure drop at the metering nozzle by means of pressure controlcomponents is excessively complex and expensive.

The aforenoted known fuel injection system has further the disadvantagethat the matching of the fuel-air ratio with the engine characteristicsdoes not follow point by point, but, because of the use of theaforenoted pressure-responsive means, it is performed in such a mannerthat the metered fuel quantity has an optimal value for some operationalconditions, whereas in wide operational ranges the fuel quantities donot correspond accurately to the requirements.

In another known fuel injection system of the type outlined hereinbeforeand disclosed, for example, in German Pat. No. 1,191,177, there isprovided a device wherein a second throttle member controls a pneumaticsetting motor which is associated with a fuel metering valve which, inturn, detennines the fuel-air ratio as a function of the pressureprevailing in the suction tube between the butterfly valve and theaforenamed second throttle member. This second throttle member isdisposed in the suction tube upstream'of' the first throttle member(i.e. the butterfly valve) and is operated'in its opening direction bythe vacuum prevailing between the two throttle members and bythepressure prevailing upstream of the second throttle member. For such asystem, too, as far as the continuous fuel injection is concerned, thedisadvantages mentioned hereinbefore apply.

OBJECT ANDSUMMARY OF THE INVENTION It is an object of the invention toprovide an improved fuel injection system from which the above-noteddisadvantages are eliminated and, particularly, as longas the engineruns hot, a near perfect combustion of the fuel is achieved with thesimplest means.

Briefly stated, according to the invention, thebias or preload on thereturn force acting on the regulator member is changed as a function ofa variable magnitude characterizing the engine operation, such as theengine temperature. The return force is supplied by a return spring, thebias or preload of which is variable by means of a temperature-dependentcontrol element, such as an expansible regulator.

The aforenoted regulator member displaces-as afunction of the flow rateof air in the suction tube and as a function of the preload on saidreturn spring-a three-dimensional cam which, in turn, adjusts a followerpin of a fuel quantity metering device. The three-dimensional cam isalso displaceablein a direction normal to the movement caused by theregulator member as a function of the setting of the butterfly valvedisposed in the suction tube.

The invention-will be better understood, as well as further objects andadvantages will become more apparent, from the ensuing detailedspecification of five exemplary embodiments taken in conjunction withthe drawing.

BRIEF DESCRIPTION OF THE DRAWINGv FIG. I is an axial sectional view of afirst embodiment of the invention;

FIG. 2 is a partial sectional view along line Il-II of FIG. 1;

FIG. 3 is a sectional view along line III-III of FIG. 2;

FIG. 4 is an axial sectional view of a second embodiment of theinvention;

FIG. 5 is an axial sectional view of a third embodiment of theinvention;

FIG. 6 is a partial sectional view along line VIVI of FIG.

FIG. 7 is a sectional view along line VII-VII of FIG. 6;

FIG. 8 is an axial sectional view of a fourth embodiment of theinvention; and

FIG. 9 is an axial sectional view of a fifth embodiment of theinvention.

DESCRIPTION OF THE EMBODIMENTS In the description which follows, theembodiments are discussed in a parallel manner. Reference numeralsindicating components of identical structure and/or function areidentical and are plain for the embodiments shown in FIGS. 1-4, but areprovided with a prime sign for the embodiments depicted in FIGS. 5-9.

In all the embodiments, the intake air flow in the direction of thearrow in the suction tube 1, l and impinges against a baffle plate 2, 2'disposed normal to the direction of air flow and forming part of apressure-responsive regulator member. The air also flows past anarbitrarily operable butterfly valve 3, 3' and proceeds to the cylindersof an internal combustion engine, not shown. In the embodiments shown inFIGS. 1-4, the baffle plate 2 is disposed upstream of the butterflyvalve 3, whereas in the embodiments shown in FIGS. 5-9, the baffle plate2 is disposed downstream of the butterfly valve 3'. In each figure thebaffle plate shown in phantom lines represents a position thereof inwhich the flow passage section is at a maximum.

As shown in FIGS. 3 and 7, the fuel is drawn from a tank 4, 4' by meansof a continuously operating pump 5, 5' and is delivered through a filter6, 6' to a schematically shown fuelmetering device 7, 7. In order tomaintain the pressure at a constant value, between the filter andfuel-metering device there is provided a pressure-limiting valve 8, 8'disposed in a return conduit. From the fuel-metering device 7, 7 thereextend several fuel conduits 9, 9' to the fuel injection nozzles l0, 10'(only one shown).

The baffle plate 2, 2' is fixedly secured to one end of a guiding rod11, 11' which is axially displaceably held in a sleeve 12, 12 mounted inthe suction tube 1, 1' coaxially and stationarily with respect thereto.The guiding rod ll, 11 is provided, at its end distal from the baffleplate 2, 2', with an axial blind bore which threadedly holds a couplingpart l3, 13'. The latter is provided with a deep annular groove 14, 14'.

Within the suction tube, perpendicularly to the longitudinal axisthereof, there is rotatably held a shaft 15, 15', the axis of whichcrosses at a distance that of the suction tube. With shaft 15, 15 thereis fixedly connected a lever 16, 16' which, by means of a lug 17, 17,projects into groove 14, 14"0f the coupling part l3, 13. To the leverl6, 16', between the shaft l5, l5 and the lug 17, 17, there is securedone end of a return spring l8, 18', which, with its other end, engages asetting lever 19, 19' pivotally supported by a stationarily held pin 20,20'. The setting lever 19, 19 is moved about the pivot 20, 20 by meansof a temperature-dependent control element 21, 21'. The force exerted bythe latter is transmitted by means of a rod 22, 22' associated with aforce accumulator 23, 23.

That portion of the suction tube which lies between the baffle plate 2,2 and the butterfly valve 3, 3' communicates, by means of a bypass 24,24, with another part of the suction tube on the opposite side of thebutterfly valve 3, 3. The lastnamed part of the suction tube isdownstream of the butterfly valve 3 in the embodiments shown in FIGS. I4and is upstream of the butterfly valve 3 in the embodiments illustratedin FIGS. 5-9, as it will be described in more detail as thespecification progresses. The flow passage section of bypass 24, 24 iscontrolled by a piston 25, 25' which is displaced together with the rod22, 22' and the force accumulator 23, 23.

In the embodiments according to FIGS. l-4, the butterfly valve 3 has asupport shaft 26 rotatably disposed in the suction tube diametricallythereof and provided, at the end outside the suction tube, with a cam 27(FIGS. 2 and 3). The cam 27 is in contact with one end of a followerlever 28 which, in turn, is swingable about a fixed pivot 29.

In the embodiments according to FIGS. 5-9, to the shaft 26 of thebutterfly valve 3' there is fixedly attached a lever 27 (shown in planview in FIG. 6) which, with a forked terminus, engages an annular grooveof an axially displaceable actuating rod 30'. The other end of thelatter has a second annular groove into which there extends a fork ofone arm of a bellcrank lever 28' swingably secured about a fixed pivotpin 29'.

The bellcrank lever 28, 28 (FIGS. 2, 3 and 6, 7) engages, by means of aroller 31, 31, a frontal face of a three-dimensional cam 32, 32 which isaxially displaceable on shaft 15, I5 against the force of a returnspring 33, 33 but which is prevented from rotating relative to saidshaft. The threedimensional cam 32, 32' is in engagement with a followerroller 35, 35 mounted on a lever 34, 34 which is pivotally secured atone end and which, with its other end, actuates a pin 36, 36' of thefuel-metering device 7, 7.

In the embodiment according to FIG. 9, the pivotal point of lever 34' isstationary during normal engine operation, but is displaced by means ofthe temperature-dependent control element 21' through a bellcrank lever38 and the extended rod 22' in order to deliver additional fuelquantities when the engine runs cold.

OPERATION OF THE EMBODIMENTS If the flow rate of intake air is increasedin the suction tube due to a rotation of the butterfly valve 3, 3', thevelocity of the air also increases in the flow passage section definedby the bafile plate 2, 2 and suction tube 1, 1. As a result, thepressure downstream of the baffle plate decreases and thus, the guidingrod 11, 11 is displaced in the sleeve 12, 12' under the effect of thealtered pressure difference upstream of and downstream of the baffleplate. The displacement of the baffle plate and the guiding rod iseffected against the force of spring 18, 18' until, due to the increasein the flow passage section, the air velocity and thus the said pressuredifference at least approximately reach their initial value. The shaft15, 15 and the three-dimensional cam 32, 32 rotate during thedisplacement of the guide rod 11, ll

As the butterfly valve 3, 3' is turned, the three-dimensional cam isaxially displaced on the shaft 15, 15' through shaft 26, 26', cam 27 (orlever 27' with the actuating rod 30'), bell crank lever 28, 28 androller 31, 31'. The fuel is metered dependent upon the flow rate of theair and upon the setting of the butterfly valve, throughthree-dimensional cam 32, 32', follower roller 35, 35', lever 34, 34',and follower pin 36, 36'.

Dependent upon the temperature of the engine, the preload on the springl8, 18' is varied by means of the temperaturedependent control element21, 21'. If the engine is cold, the said preload is small; on the otherhand, if the engine has reached the desired operational temperature, thereturn spring 18, 18 is tensioned (preloaded) to an increased extentresulting in a leaner fuel-air mixture. If the engine temperaturesincrease further, the spring 18,18 is not tensioned to a greater extentsince the lever l9, 19, when the desired temperatures are reached,engages an abutment 37, 37. Subsequent to such engagement it is solelythe force accumulator 23, 23 which takes up the expansion forces ofelement 21, 21. As soon as the desired operating temperatures arereached, the bypass 24, 24', affecting the fuel-air mixture, is closedby the piston 25, 25'.

In the embodiments according to FIGS. 1, 5 and 9, the bypass 24, 24' isadapted to establish communication between those parts of the suctiontube that are separated by the butterfly valve 3. As long as the bypass24, 24' is maintained open by piston 25 (cold engine operation), thepressure-responsive regulator member is exposed to an air quantity whichis larger than that set by the butterfly valve 3. As a result, anadditional quantity of fuel-air mixture is delivered to the engine. Thisis particularly required because of the substantial frictionalresistances prevailing in a cold engine. By an appropriate coordinationof the temperature-dependent preload on the spring 18 and the traveledpath of the piston 25, a desired ratio of fuel and air density may beobtained.

In the embodiments according to FIGS. 4 and 8, there is provided anadditional possibility for affecting the aforenoted ratio. One part ofthe intake air, prior to its flowing past the butterfly valve or theregulator member, is directed through the bypass from the first sectionof the suction tube to the last section thereof as long as the engine iscold. The air channeled in this manner has thus no effect on the settingof the regulator member and therefore has no effect on the metered fuel.

The embodiments in which the regulator member is disposed downstream ofthe butterfly valve (FIGS. 5-9), have, with respect to the otherembodiments, the disadvantage that the shafts 15, 15 and 26, 26' arespaced relatively far from one another and require a linkage means 30'.The embodiments according to FIGS. 5-9 have, however, the advantage thatthe regulator member, due to the pulsating air flow through the enginecylinders, is in continuous oscillation so that the guide rod 11 ismoved substantially without hysteresis losses in the sleeve 12'.

In the last embodiments (according to FIGS. 5-9), during idling, thatis, when the butterfly valve 3 is almost closed, the density of the airflow effecting the motion of the regulator member changes downstream ofthe butterfly valve by virtue of the vacuum generated by the engine inthe suction tube. Therefore, the three-dimensional cam 32' should bedesigned for this range in such a manner that small displacements of theregulator member from its position of rest cause no change in the fuelquantities. in order to obtain during cold engine operation animprovement of the fuel-air mixture, even in the aforenoted range, thepivotal point of the lever 34' is changed by means of thetemperature-dependent control element through the bellcrank lever 38 andthe rod 22.

The advantages of the fuel injection system according to the inventionreside particularly in that by means of the combination of thepressure-responsive regulator member with the three-dimensional camadapted to the engine characteristics, the fuel may be metered in a veryaccurate manner. MOre particularly, in the individual operation ranges(full load, partial load, idling) the desired mixture ratio (rich orlean) may be set by controlling the preload of the return spring of theregulator member and controlling a bypass of the suction tube with theaid of temperature-dependent means in such a manner that a desired richmixture is obtained when the engine runs hot.

What is claimed is:

1. In a fuel injection system for internal combustion engines, saidsystem being of the known type that includes (A) a suction tube fordrawing intake air, (B) an arbitrarily operable throttle means disposedin said suction tube for controlling the supply of said air, (C) aregulator member at least partially disposed in said suction tube anddisplaceable therein the response to the pressure of air, said regulatormember, dependent upon the flow rate of air determined by said throttlemeans, varies a flow passage section in said suction tube, saidregulator member, dependent upon said flow passage section and by virtueof its displacement, continuously meters fuel by actuating a variablefuel throttle through which the fuel flows with a constant pressure dropand (D) means supplying a return force exerted on said regulator memberand opposing the displacement thereof by said pressure, the improvementcomprising A. a fuel-metering device having a following member, thedisplacement of which determines the fuel quantities delivered by saidfuel-metering device,

B. a rotatably and axially displaceably held three-dimensional camconnected with said follower member, said cam is operatively connectedwith said regulator member and is rotatable thereby, said cam isoperatively connected with said arbitrarily operable throttle means andis axially displaceable thereby and C. means for varying the preload onsaid return force as a function of a variable dependent upon theoperation of said engine.

2. An improvement as defined in claim 1, wherein said means for varyingthe preload on said return force is a temperature-dependent controlelement, said improvement further includes A. a lever pivotable about anaxis, said three-dimensional cam is connected with said follower memberthrough said lever, said lever is operatively connected with saidtemperature-dependent control element and displaceable thereby to shiftsaid last-named axis parallel to itself,

B. a bypass interconnecting portions of said suction tube and C. meansconnecting said temperature-dependent control element with said bypassto establish and break communication between said portions in responseto the temperature of said engine.

3. An improvement as defined in claim 15, wherein said regulator memberincludes A. a baffle plate disposed in said suction tube normal to theflow of said air therein,

B. a guide rod fixedly attached to said baffle plate and extendingparallel with the flow of said air and C. a guide sleeve fixedly heldwithin said suction tube coaxially therewith, said guide sleeve slidablyreceives said guide rod.

4. An improvement as defined in claim 3, including A. a lever connectedto said guide rod and turnab e thereby and B. a shaft affixed to saidlever and rotatable thereby, said three-dimensioned cam is axiallyslidably mounted on said shaft and is constrained to rotate therewith asa unit.

5. An improvement as defined in claim 4, wherein said means supplyingsaid return force is a spring, said means for varying the preload onsaid spring is a temperature-dependent control element; one end of saidspring is attached to said lever, the other end of said spring isattached to an additional lever displaceable by saidtemperature-dependent control element for varying the preload on saidspring.

6. An improvement as defined in claim 3, including A. a shaft rotatablyheld in said suction tube and carrying a throttle member fixedlyattached thereto and forming part of said arbitrarily operable throttlemeans,

B. a cam affixed to said shaft and rotating therewith in unison,

C. a level pivotable about a stationary axis, one end of said levercarries a follower in engagement with said lastnamed cam, the other endof said lever is in engagement with said three-dimensional cam todisplace the latter axially dependent upon the rotation of said shaftand D. a spring in engagement with said three-dimensional cam to opposethe axial displacement of the latter caused by said lever.

1. In a fuel injection system for internal combustion engines, saidsystem being of the known type that includes (A) a suction tube fordrawing intake air, (B) an arbitrarily operable throttle means disposedin said suction tube for controlling the supply of said air, (C) aregulator member at least partially disposed in said suction tube anddisplaceable therein the response to the pressure of air, said regulatormember, dependent upon the flow rate of air determined by said throttlemeans, varies a flow passage section in said suction tube, saidregulator member, dependent upon said flow passage section and by virtueof its displacement, continuously meters fuel by actuating a variablefuel throttle through which the fuel flows with a constant pressure dropand (D) means supplying a return force exerted on said regulator memberand opposing the displacement thereof by said pressure, the improvementcomprIsing A. a fuel-metering device having a following member, thedisplacement of which determines the fuel quantities delivered by saidfuel-metering device, B. a rotatably and axially displaceably heldthree-dimensional cam connected with said follower member, said cam isoperatively connected with said regulator member and is rotatablethereby, said cam is operatively connected with said arbitrarilyoperable throttle means and is axially displaceable thereby and C. meansfor varying the preload on said return force as a function of a variabledependent upon the operation of said engine.
 2. An improvement asdefined in claim 1, wherein said means for varying the preload on saidreturn force is a temperature-dependent control element, saidimprovement further includes A. a lever pivotable about an axis, saidthree-dimensional cam is connected with said follower member throughsaid lever, said lever is operatively connected with saidtemperature-dependent control element and displaceable thereby to shiftsaid last-named axis parallel to itself, B. a bypass interconnectingportions of said suction tube and C. means connecting saidtemperature-dependent control element with said bypass to establish andbreak communication between said portions in response to the temperatureof said engine.
 3. An improvement as defined in claim 15, wherein saidregulator member includes A. a baffle plate disposed in said suctiontube normal to the flow of said air therein, B. a guide rod fixedlyattached to said baffle plate and extending parallel with the flow ofsaid air and C. a guide sleeve fixedly held within said suction tubecoaxially therewith, said guide sleeve slidably receives said guide rod.4. An improvement as defined in claim 3, including A. a lever connectedto said guide rod and turnable thereby and B. a shaft affixed to saidlever and rotatable thereby, said three-dimensioned cam is axiallyslidably mounted on said shaft and is constrained to rotate therewith asa unit.
 5. An improvement as defined in claim 4, wherein said meanssupplying said return force is a spring, said means for varying thepreload on said spring is a temperature-dependent control element; oneend of said spring is attached to said lever, the other end of saidspring is attached to an additional lever displaceable by saidtemperature-dependent control element for varying the preload on saidspring.
 6. An improvement as defined in claim 3, including A. a shaftrotatably held in said suction tube and carrying a throttle memberfixedly attached thereto and forming part of said arbitrarily operablethrottle means, B. a cam affixed to said shaft and rotating therewith inunison, C. a level pivotable about a stationary axis, one end of saidlever carries a follower in engagement with said last-named cam, theother end of said lever is in engagement with said three-dimensional camto displace the latter axially dependent upon the rotation of said shaftand D. a spring in engagement with said three-dimensional cam to opposethe axial displacement of the latter caused by said lever.